in pyt (Python Toolbox) why can't I make the parameter Optional?

When defining parameters in a .pyt (Python toolbox) I would like to make one of the parameters optional - I think.

It's a boolean parameter, allowing the user to specify weather the tool is allowed to overwrite certain values.

I have made it default to False, and that would be the correct setting in 9 of 10 cases, so I would prefer if the tool would be able to just go with this default value. Unfortunately, when run, the tool insist that I toggle the boolean, before it will remove the little green dot. If I run the tool with the default values untouched, it gives me an error-box saying: "ERROR 000735: Overwrite Existing OBJNAM and NOBJNM: Value is required"

I have tried to change the parameter from parameterType="Required", to parameterType="Optional", but it seems to have no effect on the tool behaviour.

I checked some of my code in a Python toolbox and was wondering if you can solve the problem by simple omitting the line param3.value = "False". The standard behaviour as far as I can see is anyway to have the checkbox unchecked. When I force my optional parameters to be true by setting param3.value = "True" then it works without any problems.